1. Field of the Invention
The present invention relates to a key signal processing apparatus for video signal processing used in digital video signal switchers etc. for processing a key signal for giving a special effect to a video signal.
The present invention more particularly relates to a key signal processing apparatus for video signal processing which produces a key signal enabling a special effect at a sub-pixel size smaller than an interval between pixels.
The present invention further particularly relates to a key signal processing apparatus for video signal processing suitable for processing a key signal enabling softened borderline, a key signal enabling softened drop-border, etc.
Further, the present invention relates to a key signal processing apparatus for video signal processing able to be configured as an IC circuit suitable for multiple-processing (composition) of key signals.
More specifically, the present invention relates to a key signal processing apparatus for video signal processing suitable for producing a key signal for defocusing a video signal.
2. Description of the Related Art
In a digital video signal switcher, a video signal is given various special effects. These special effects include for example borderlines, drop-borders, shadows, outlines, etc. Key signals are used for applying such special effects. Various kinds of processing need to be performed on key signals according to the special effects.
When applying sophisticated special effects, special effects less than the pixels of the video signal, that is, special effects of the sub-pixel level, are demanded. In the past, however, no circuit (apparatus) of a simple configuration was known for effectively processing key signals for such special effects.
Further, in the past, when synthesizing a signal from two key signals, for example, when performing positive non-additive mixing (NAM) computation for increasing the pulse width of a key signal, if the times (phases) of the two key signals were too far apart, then the result would be the same as with output of the two key signals separately and the pulse width of the key signal could not be increased as desired, that is, the desired signal synthesization could not be performed.
There is still not known any key signal processing apparatus for video signal processing suitable for processing a key signal enabling softened borderline or a key signal enabling softened drop-border, which are expansions of such processing.
Furthermore, a key signal processing apparatus for video signal processing of a configuration suitable for complex (multiple) and effective processing of key signals such as softened borderline or softened drop-border has not been known either.
Also, a key signal processing apparatus for video signal processing which can produce a key signal when a special effect for giving smooth borderlines is required, has not been known either.
Further, a key signal processing apparatus for video signal processing which provides a smoothly changing defocused key signal has not been known either.